About

Ashley Jernigan is an Assistant Professor in the School of Plant and Environmental Sciences at Virginia Tech, located at 406 Price Hall, Blacksburg, VA. Her research focuses on developing an understanding of soil biological processes to improve the sustainability of cropping systems. As an agroecologist, she takes a systems-level perspective to crop nutrition and pest management, aiming to bridge ecological mechanisms with crop management practices. Her expertise includes organic agriculture, soil ecology, and agroecosystem modeling, and she emphasizes interdisciplinary research in her work. Dr. Jernigan holds a Ph.D. in Entomology from Cornell University, earned in 2023, and a B.S. in International Agriculture and Rural Development from Cornell University, completed in 2016. Her appointment at Virginia Tech is divided into 60% research, 30% teaching, and 10% service. She is actively involved in extension activities through Virginia Cooperative Extension Local Offices and Virginia Agricultural Experiment Station Agricultural Research and Extension Centers. Her contact information includes email ajernigan@vt.edu and phone number 540-231-6761.

Research topics

• Ecology
• Biology
• Agronomy
• Environmental science
• Agroforestry

Selected publications

• Effects of soil biofumigation on non-target springtails (Collembola) and earthworms (Opisthopora)

  Scientific Reports · 2026-01-06

  articleOpen access

  Soil health is supported by diverse communities of organisms, including springtails and earthworms, facilitating essential processes such as nutrient cycling, organic matter decomposition, and soil structure maintenance. Cultural control methods promoted through Integrated Pest Management (IPM) are often assumed to be environmentally friendly, and their potential effects on soil health have received limited attention. Biofumigation, a cultural tactic, utilizes cruciferous plants like Brassica juncea (Brassicales: Brassicaceae), or their byproducts, to control soil-borne pests, yet their impacts on non-target organisms remain understudied. In this greenhouse study, we evaluated the impact of soil biofumigation with brown mustard seed meal (BMSM) on the springtail Folsomia candida (Entomobryomorpha: Isotomidae) and the earthworm Eisenia fetida (Opisthopora: Lumbricidae). An 85% reduction in springtail populations was recorded within 1 h of BMSM application. However, the springtail population recovered and surpassed the number of springtails in untreated media after 26 days. Earthworms preferred untreated media over BMSM-treated media immediately after incorporation. However, earthworms reared in the biofumigated media had higher body weight and produced more viable cocoons compared to those reared in untreated media. The negative effects of biofumigation on springtails and the deterrence of earthworms appeared to be short-lived and may later contribute to their reproductive fitness.

  PublisherOA PDFDOI

• Evaluating the environmental preferences and spread of the invasive Asian Jumping Worm (Amynthas spp.) in southwestern Virginia

  PubMed · 2026-01-06

  articleOpen accessSenior author

  Asian Jumping Worms (AJW) are an invasive species in North America that can negatively impact soil habitats. This study investigated AJW environmental preferences, movement over time, and overwintering ability in Virginia, USA. Worms were sampled on four dates, two in fall 2024 and two in spring 2025, in four areas with different environmental conditions: (1) well-drained, shady (2) well-drained, mid-day sun (3) moist, shady (4) well-drained, early sun. Results indicate AJW may have delayed invasions in mulched landscapes and a preference for well-drained soil. These findings increase our understanding of AJW environmental patterns, which may help stop their spread.

  PublisherOA PDFDOI

• Where Are We Today? State of Organic Agriculture Education and Technical Programs: Proceedings from the ASHS Organic Interest Group 2025 Workshop

  HortTechnology · 2026-03-10

  articleOpen access1st authorCorresponding

  Universities vary greatly in their organic agriculture education programs, with differences in student interest in studying organic production and food systems, classes offered, and infrastructure and facilities. The organic agriculture curriculum options are also evolving as a result of departmental or college-level curriculum revisions. Similarly, the technical assistance provided for growers varies from state to state. Recent US Department of Agriculture–Agricultural Marketing Service Transition to Organic Partnership Program programming has created more interest in providing and growing this assistance. The workshop “Where are we today? State of Organic Education and Technical Programs” was conducted at the 2025 American Society for Horticultural Science Conference in New Orleans, LA, USA, and featured a panel of teaching and extension scholars who provided insights into the existing programs and challenges that are currently affecting organic production across the United States. This workshop focused on discussing the challenges to organic agriculture education both at the undergraduate and farmer levels, and opportunities for growth.

  PublisherDOI

• Common soil invertebrate (Collembola: Isotomiella minor) reduces weed biomass and alters weed communities

  Applied Soil Ecology · 2025-05-19

  articleOpen access1st authorCorresponding

  Soil microarthropods affect soil ecosystems in a manner that may contribute to balancing the goals of building soil health and controlling weeds in organic agricultural systems. While soil microarthropod feeding behavior can affect plant growth, their impacts on plant communities in agricultural systems are largely unknown. A greenhouse experiment was conducted to investigate the impacts of microarthropods on weed communities. A model weed seed bank was used in each mesocosm, which included yellow foxtail ( Setaria pumila (Poir.) Roem&Schult.), giant foxtail ( Setaria faberi Herrm.), Powell amaranth ( Amaranthus powellii S. Watson ), waterhemp ( Amaranthus tuberculatus (Moq.) Sauer), common lambsquarters ( Chenopodium album L.), and velvetleaf ( Abutilon theophrasti Medik.). The study included three treatments: Collembola ( Isotomiella minor , Schaffer 1896) abundance (none, low, high), soil microbial community (sterilized/non-sterilized), and fertilizer (presence/absence of compost). A lab experiment examining individual weed species interactions with I. minor was conducted to elucidate the mechanisms driving the greenhouse experiment findings. Twenty seeds of each weed species were placed on moistened germination paper in containers with varying I. minor abundance levels (none, low, high, very high). Seed germination was recorded after five and seven days. In the greenhouse, the presence of I. minor increased total weed emergence during the first two weeks, but this effect diminished after three weeks. Increasing I. minor abundances generally decreased weed biomass, though this effect was greater in the non-sterilized soil. In the non-sterilized soil, I. minor presence decreased total aboveground weed biomass production by up to 23 %. The Amaranthus species, Powell amaranth and waterhemp, drove this effect with a 55 % and 32 % reduction in biomass, respectively. In tandem, the Amaranthus species had reduced abundances in the presence of I. minor . I. minor increased yellow foxtail germination in the lab, while not affecting the other weed species. This suggests that their effects on the Amaranthus weeds in the greenhouse were likely not caused by direct effects on germination, but instead through nutrient cycling or root herbivory. The proposed mechanism underlying these interactions is that I. minor can initially stimulate germination by feeding on seed coats, but when the seed coats are minimal can damage the seedling. Our findings indicate I. minor could impact weed growth in a manner that affects management decisions and outcomes. • Isotomiella minor decreased total aboveground weed biomass production by up to 23 %. • Powell amaranth (55 %) and waterhemp (32 %) biomass were most decreased by I. minor . • I. minor directly increased yellow foxtail germination in lab study. • Seed coat composition may influence the outcomes of seed-Collembola interactions.

  PublisherDOI

• Common Soil Invertebrate (Collembola: Isotomiella Minor) Reduces Weed Biomass and Alters Weed Communities

  2024

  1st authorCorresponding
  • Agronomy
  • Biology
  • Ecology
  PublisherDOI

• Fertility and tillage intensity affect weed community diversity and functional structure in long‐term organic systems

  Ecological Applications · 2024 · 3 citations

  • Agronomy
  • Biology
  • Environmental science

  Abstract Knowledge of how agricultural management interacts with weed seed banks and emergent weed communities is crucial for proactive weed management. Though studies have detailed how differences in disturbance and nutrient applications between organic and conventional herbicide‐based systems affect weed communities, few have focused on these same factors in contrasting organic systems. This study assessed the seed banks and emergent weed communities from the most recent crop rotation cycle (2017–2022) of a long‐term experiment, which compared four organic grain and forage cropping systems differing in nutrient inputs and soil disturbance. The high fertility (HF) system received high‐rate nutrient applications, low fertility (LF) received low‐rate applications, enhanced weed management (EWM) focused on weed control through frequent soil disturbance, and reduced tillage (RT) prioritized soil health with less intense or frequent soil disturbance. Soil samples for greenhouse germination assays were collected at the beginning (2017) and end (2022) of the rotation to explore how these four systems influenced seed bank dynamics over time. Weed community biomass was also sampled in each crop during this time. Treatment effects on weed abundance, taxonomic diversity, and community‐weighted means and functional dispersion of weed traits were analyzed with generalized mixed‐effect models. The RT system had the highest weed seed bank taxonomic diversity, and EWM had the lowest. RT and LF had higher functional dispersion of traits than HF in the seed bank. Weed seed bank communities in HF and RT were characterized by short, small‐seeded, and early germinating weed species. However, seed banks were also labile: Differences between systems in seed density and all other mean trait values were dependent on the crop, which preceded seed bank sampling. Likewise, differences among emergent weed communities in the four systems depended on an interaction between crop species and their planting year. Results suggest that resource availability and intensity of disturbance act as weed community assembly filters in organic cropping systems. Organic growers seeking to design systems that balance weed management and production goals can use relatively low soil disturbance and nutrient application to increase weed community taxonomic or functional diversity without necessarily increasing weed biomass or seed bank density.

  PublisherOA PDFDOI

• Microarthropods improve oat nutritional quality and mediate fertilizer effects on soil biological activity

  Agronomy Journal · 2024-05-27 · 2 citations

  articleOpen access1st authorCorresponding

  Abstract Soil biological processes are important drivers of crop productivity in agroecosystems. Soil microarthropods play key roles in nutrient cycling and plant nutrient acquisition, though little is known about how these effects manifest in crop production under different organic fertilizer amendments. We explored the interactive effects of microarthropods and fertilizers on crop productivity in two greenhouse experiments: experiment one involved a single Collembola species, and experiment two involved diverse microarthropod communities. Oats were grown as a model crop in both experiments under one of three initial fauna abundance levels (none, low, and high). In both experiments, four organic fertilization treatments were compared: alfalfa green manure, Kreher's Poultry Litter Compost, Chilean nitrate, and a nonamended control. Oat growth and development were evaluated weekly. During each experiment, 48 pots were selected randomly for destructive harvest at two separate times to mimic forage and grain harvest stages. At each harvest, multiple soil metrics (microarthropods, microbial biomass, microbial enzymes, and soil carbon and nitrogen) and plant metrics (biomass, reproduction, and tissue carbon and nitrogen content) were evaluated. Our findings indicated that microarthropods, both single species and diverse communities, stimulated nitrogen cycling and enhanced crop nutrient status. As microarthropod abundance and diversity increased, microarthropods exerted more effects on soil microbial activity. The effects of the microarthropods enhance the breakdown of fertilizers, ultimately making fertilizer choice less important for soil processes and plant nutrient availability. Our findings suggest that microarthropods drove oat production yields primarily through their effects on soil biological processes.

  PublisherOA PDFDOI

• Spatial and temporal dynamics of Collembola (Isotomiella minor) and plant pathogenic fungi (Rhizoctonia solani) interactions

  Applied Soil Ecology · 2024-07-02 · 1 citations

  articleOpen access1st authorCorresponding

  The mechanistic and spatial dynamics of microarthropod-plant pathogen interactions remain understudied, despite the importance of these interactions in plant disease control. We conducted three complementary laboratory experiments using the plant-pathogenic fungus, Rhizoctonia solani, and the Collembola Isotomiella minor. The dominant mechanism (consumption vs. dispersal) of these interactions was investigated over 5 days in a controlled environment. The dominant mechanism observed was consumption, with I. minor decreasing R. solani growth by up to 58 %. There was no evidence of pathogen dispersal, however, there was potential for R. solani dispersal by I. minor as there were viable pathogen structures on the cuticle and in the frass. I. minor effects on R. solani mycelial growth rate were then determined using race tubes over 14 days. I. minor decreased R. solani mycelial growth rate by up to 23 %. Soil environment effects were explored over 5 days in a controlled environment using mineral substrate to mimic a 3-dimensional soil environment, both with and without organic matter (alfalfa) additions. In the soil without organic matter, the high I. minor abundances decreased R. solani growth compared to the low and no I. minor abundances by 23 % and 22 % respectively. In the soil with organic matter, I. minor did not affect R. solani growth. These findings suggest that organic matter in soils may be diminishing collembolan control of plant pathogens in field settings.

  PublisherDOI

• Soil Microarthropods Improve Oat Nutritional Quality and Mediate the Effects of Fertilizers on Soil Biological Activity

  SSRN Electronic Journal · 2023-01-01

  preprintOpen access1st authorCorresponding
  PublisherDOI

• Soil microarthropod effects on plant growth and development

  Plant and Soil · 2022 · 21 citations

  1st authorCorresponding
  • Biology
  • Ecology
  • Agronomy
  PublisherDOI

Frequent coauthors

• Stéphane Cordeau

  Agroécologie

  20 shared

• Matthew R. Ryan

  New York State College of Agriculture & Life Sciences

  18 shared

• Charles L. Mohler

  Cornell University

  17 shared

• Antonio DiTommaso

  Cornell University

  17 shared

• Brian Caldwell

  Cornell University

  17 shared

• Laurie E. Drinkwater

  New York State College of Agriculture & Life Sciences

  16 shared

• Sarah J. Pethybridge

  Cornell University

  7 shared

• Kyle Wickings

  6 shared

Education

• Doctor of Philosophy, Entomology

  Cornell AgriTech

• Bachelor of Science, International Agriculture and Rural Development

  Cornell University

  2016